It is known that an aromatic primary amine color developing agent oxidized with exposed silver halide as an oxidizing agent reacts with a coupler to form a dye such as an indophenol, an indoaniline, an indamine, an azomethine, a phenoxazine, a phenazine and the like, thus forming a color image. In order to form a magenta color image, a 5-pyrazolone type coupler, a cyanoacetophenone type coupler, an indazolone type coupler, a pyrazolobenzimidazole type coupler or a pyrazolotriazole type coupler is employed.
Magenta color image forming couplers which have been widely used in practice and on which various investigations have been made are almost all 5-pyrazolones. However, it is known that dyes formed from 5-pyrazolone type couplers have an undesirable absorption of yellow component in the region around 430 nm, which causes color turbidity.
In order to reduce yellow component absorption, a pyrazolobenzimidazole nucleus as described in British Patent 1,047,612, an indazolone nucleus as described in U.S. Pat. No. 3,770,447 and a 1H-pyrazolo[5,1-c]-1,2,4-triazole nucleus as described in U.S. Pat. No. 3,725,067 have been proposed as a magenta color image forming coupler skeleton. Further, an imidazopyrazole nucleus as described in JP-A-59-162548 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), a 1H-pyrazolo[1,5-b]-1,2,4-triazole nucleus as described in JP-A-59-171956 and a pyrazolotetrazole nucleus as described in JP-A-60 33552 have been recently proposed as novel magenta color image forming coupler skeletons.
On the other hand, in order to save on the amount of silver used in color light-sensitive materials, while responding to the need for rapid processing and improved preservability of color light-sensitive materials, so-called two-equivalent couplers having a releasing group at the dye forming position of the coupler skeleton have been investigated.
5-pyrazolone type couplers having a releasing group connected to the dye forming position through a sulfur atom are known and described in many patents. However, many of these couplers have difficulties in that they have low color forming properties. For instance, they are apt to cause the formation of fog, they cause silver halide to degrade photographic properties, they adversely affect fastness of color images, and they are unstable per se. For such reasons they have not been employed in practice.
The couplers as described in U.S. Pat. No. 4,351,897 are superior in view of overcoming these disadvantages. However the problem of color turbidity is still present in these couplers. Further, they have a problem in that density color image is reversed particularly at the high density portion (Dm inversion). In order to solve these problems, it is necessary to employ a fine grain emulsion, etc.
Recently, the couplers described in WO 88/04795 have been disclosed. They have a good color forming property particularly in rapid processing and the inversion at the high density portion is restrained without using a fine grain emulsion. However, the problem of color turbidity is still not solved with these couplers. Further, they tend to form color in unexposed portions, resulting in the formation of so-called fog.
Among pyrazoloazole type couplers with which the problem of color turbidity is prevented, those having a releasing group connected to the dye forming position through a sulfur atom are described, for example, in JP-A-62-186262, JP-A-62-209457 and JP-A-63-41851. These couplers exhibit improved color forming properties and fastness of color image formed therefrom, but the same are still insufficient. In particular, the color forming property is inferior in case of rapid processing and sufficiently high color density can not be obtained. Moreover, it has been desired that couplers formed therefrom exhibit more improved fastness of color image.
As described above, it has been desired to provide couplers having good color reproducibility (due to the same being free from the undesirable subsidiary absorption of the dye formed therefrom). Also, it has been desired to provide couplers having a high color forming rate and which can provide a sufficiently high color density even under condition where the amount of silver employed in the light sensitive material is reduced or the light-sensitive material is subjected to rapid processing. Further, it has been desired to provide the same while producing a low level of fog. Furthermore, a silver halide color photographic material containing a coupler capable of forming color image having improved fastness has been desired.